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Demisable Reaction-Wheel Assembly

Tuesday, 25 November 2008

A document discusses the concept of a
demisable motor-drive-and-flywheel
assembly [reaction-wheel assembly
(RWA)] used in controlling the attitude
of a spacecraft. “Demisable” as used here
does not have its traditional legal meaning;
instead, it signifies susceptible to
melting, vaporizing, and/or otherwise
disintegrating during re-entry of the
spacecraft into the atmosphere of the
Earth so as not to pose a hazard to anyone
or anything on the ground. Prior
RWAs include parts made of metals
(e.g., iron, steel, and titanium) that melt
at high temperatures and include structures
of generally closed character that
shield some parts (e.g., magnets) against
re-entry heating.

In a demisable RWA, the flywheel
would be made of aluminum, which
melts at a lower temperature. The flywheel
web would not be a solid disk but
would have a more open, nearly-spoke-like
structure so that it would disintegrate
more rapidly; hence, the flywheel
rim would separate more rapidly so that
parts shielded by the rim would be
exposed sooner to re-entry heating. In
addition, clearances between the flywheel
and other components would be
made greater, imparting a more open
character and thus increasing the exposure
of those components.

This work was done by Russell Roder and
Eliezer Ahronovich of Goddard Space Flight
Center and Milton C. Davis III of Purdue
University.
GSC-14845-1

This Brief includes a Technical Support Package (TSP).

Demisable Reaction-Wheel Assembly (reference GSC-14845-1) is currently available for download from the TSP library.

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